Automated visualization of steel structure coating thickness using line laser scanning thermography

This paper proposes a line laser scanning thermography system for automated visualization of coating thickness distribution within a steel structure. In the proposed system, a line laser scans the coated steel structure and generates heat energy on the coating surface; the resultant heat response is measured using an infrared camera. Thereafter, the proposed coating thickness visualization algorithm quantifies and visualizes the coating thickness distribution over the entire scanned surface. The proposed system achieves (1) noncontact and nondestructive inspection of invisible coating thickness; (2) automated coating thickness inspection of steel bridges; (3) quantification and visualization of coating thickness via algorithms based on laser-induced heat transfer analyses within the coating layer. The performance of the proposed line laser scanning thermography system was validated through laboratory and field tests. The coating thickness was quantified and visualized with an accuracy of approximately 20 μm.